1993 Volume 44 Issue 2 Pages 91-96
A high dose of 6,400μg minocycline was initially injected subcutaneously into the back of the neck of a ddY mouse. Then 3,400μg were given every 12hr for 4 days. After 34hr from the first injection with minocycline Rickettsia tsutsugamushi (Rt) infected unfed larvae of L. fletcheri were attached to the mouse, and it was successful in killing Rt in mites. Out of 80 unfed larvae transferred into the ear lobe of the mouse with a fine paint brush under a stereomicroscope, 50 engorged larvae were recovered. Out of the 50,23 larvae developed into adults. Among them, 8 females (Parent generation) laid and average of 122.3 eggs (F_1), the number of laid eggs ranging from 34 to 230. The number of laid eggs was almost similar to the 133.5 eggs per Rt infected female, but less than the 170.9 eggs per Rt uninfected female. The females of L. fletcheri in the Rt infected colony produced only females, but uninfected females produced different sexes of progeny, i.e., females alone, males alone or both sexes in varied proportions by individual females. All of the F_1 larvae from the above mentioned P generation developed into only females, and males were found in F_2 for the first time in this infected colony after killing Rt at the P generation. The ratio of male to female was 297 : 4 (or 74.3 : 1). These data suggest that the presence of Rt in the ovary has a restraining effect on the birth of male progeny in the infected colony, because the sex of F_1 was determined to be female even though Rt was killed in the larval stage of the Parent generation.
